Reproducible softlock on iOS

After performing the repro steps, screen will softlock unless you perform the "slide from 3 to 4, then back to 3" steps.  Appears to be an iOS system bug, but see if we can find a workaround.

Observe the picture attached, and instructions:

• Put right finger on 1, slide up to 2 reasonably quickly

• The moment your right finger reaches 2, place your left finger on 3 and slide down to 4 reasonably quickly; this should pull down the notification window and pause rendering

• Wait for half a second or more

• Slide your left finger back up to 3 and release; rendering will not resume

• Release your right finger

If you've done it right, the game is now frozen and no longer updating its screen. It's "temporarily" because you can undo this; slide from 3 to 4, then back up to 3, then let go, and it'll unlock itself in a second or two.

Things to note:

• You do actually have to pause at 4. If you don't, it doesn't cause the problem.

• This happens only if you swipe from 1 to 2 up. It does not work if you try swiping to the side or down.

• The timing is a little finicky, but once you get the hang of it, you can reproduce it reliably (90%+).